Abstract: Welding techniques and processing for zircaloy-2 pressure tube assembly are studied. A self-made complete enclose Ar protecting device and a metal tyre have been used, by which both inside and outside welding seam areas are maintained under the laminar flow of Ar protecting environment all the time.It provents the invision of the air,and minimizieg the influences of H.O and N.The unstraightness of the welded assembly is less than or equal to 0.7‰. The welding seam is up to the first class standard. Its mechnical properties, corrosion behavior and resistance to water scouring also have reached to the specification for Zr materials used in nucleu reactars.It procides effective method for welding zircaloy-2 tubes with bigger dimensions.